Chemical Properties of Carboxylic Acids

If you leave wine standing open to the air, oxygen from the
air will oxidize the ethanol to ethanoic acid, forming
vinegar.

+ 2[O]  +

ethanol oxygen ethanoic acid water

In fact, any carboxylic acid can be made by oxidizing the
corresponding alcohol.

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Carboxylic acids can be produced from the oxidation of
alcohol.
Q)Name the carboxylic acid made when methanol is

oxidized?
A) Methanoic acid.

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• Ethanoic acid, CH3COOH is produced when ethanol, C2H5OH is
oxidised by oxidising agents,such as acidified potassium

manganate(VII),KMnO4 solution or acidified potassium dichromate(VI),
K2Cr2O7 solution through the reflux method.

• The mixture of ethanol and acidified potassium

dichromate(VI), K2Cr2O7 solution is refluxed.
• On heating, the ethanol is oxidized to ethanoic

acid, CH3COOH. K2Cr2O7 /H+ CH3COOH + H2O

C2H5OH + 2[O] Ethanoic acid

Ethanol

• The Liebig Condenser is fixed vertically to the

round bottom flask so as to condense the

ethanol vapour into liquid which is then flow

back into the flask to complete the reaction.

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• The chemical properties of carboxylic acids are studied through the
chemical reactions of ethanoic acid, CH3COOH.

• The chemical properties of carboxylic acids are determined by the
carboxyl, COOH functional group.

• Two important chemical reactions of carboxylic acids:

Chemical reactions

Reaction as an acid Reaction with alcohol

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• Ethanoic acid, CH3COOH, is a weak acid
• Ethanoic acid ionises partically in water to produce little

hydrogen ion, H+

H2O CH3COO – + H+

CH3COOH ⇌ ethanoate ion hydrogen ion

ethanoic acid

• Chemical properties of ethanoic acid are similar with
acids such as hydrochloric acid, HCl

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a) Carboxylic acid + Base → Carboxylate salt + Water

- Neutralisation reaction
- Form salt and water

Reaction between ethanoic acid, CH3COOH and copper(II) oxide,
CuO produces copper ethanoate, (CH3COO)2Cu and water, H2O

2 CH3COOH + CuO  (CH3COO)2Cu + H2O

Ethanoic Copper copper
acid oxide ethanoate

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a) Carboxylic acid + Base → Carboxylate salt + Water

Reaction between ethanoic acid, CH3COOH and sodium
hydroxide produces sodium ethanoate, CH3COONa and water, H2O

White solid is formed

CH3COOH + NaOH → CH3COONa + H2O

Ethanoic Sodium Sodium ethanoate

acid hydroxide

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b) Carboxylic acid + Metal carbonate → Carboxylate salt + Water +
Carbon dioxide

CH3COOH + CaCO3 Limewater turns chalky

2 CH3COOH + CaCO3  (CH3COO)2Ca + CO2 + H2O

Ethanoic Calcium Calcium
acid carbonate ethanoate

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c) Carboxylic acid + Metal → Carboxylate salt + Hydrogen
- such as magnesium and zinc
- Form salt and hydrogen gas

A ‘pop’ sound is heard

2 CH3COOH + Mg → (CH3COO)2 Mg + H2

Ethanoic magnesium Magnesium
ethanoate
acid

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Carboxylic acids react with alcohols to produce esters and
water.

This reaction is called esterification, with the presence of
concentrated sulphuric acid, H2SO4 as a catalyst.

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Esterification reaction

• When a mixture of glacial ethanoic acid, CH3COOH
and ethanol, C2H5OH, with a few drops of
concentrated sulphuric acid, H2SO4, is heated, an
ester called ethyl ethanoate, CH3COOC2H5 is formed.

• Ethyl ethanoate, CH3COOC2H5 is a colourless liquid that has the sweet
fruity smell and insoluble in water. Ethyl ethanoate CH3COOC2H5 floats,
forming a layer on the surface of the water.

• Concentrated sulphuric acid, H2SO4 is a catalyst in the esterification
reaction.

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Procedure:

A)

1. About 10 cm3 of dilute ethanoic acid is poured into a boiling tube.
2. A piece of magnesium ribbon is cleaned with sandpaper.
3. The magnesium ribbon is added to the ethanoic acid in the boiling

tube.
4. A lighted wooden splinter is placed at the mouth of the boiling tube.
5. All changes in the reaction are recorded.

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B)

1. About 10 cm3 of dilute ethanoic acid is poured into a boiling tube.
2. A spatula of sodium carbonate is added to the ethanoic acid.
3. The boiling tube is closed with a stopper with a delivery tube.
4. Channel the gas that is released into the lime water.
5. All the changes in the reaction are recorded.

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C)

1. A small spatula of copper(ll) oxide powder is added to 10 cm3
of ethanoic acid in a boiling tube.

2. The mixture is heated gently and stirred well with a glass rod
until no further changes occur.

3. All the changes in the reaction are recorded.

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Observation:

Reaction Observation Inference

Ethanoic acid + Effervescence occurs. Hydrogen gas is
magnesium ribbon Colourless gas released gives produced.
a ‘pop’ sound when tested with
a lighted wooden splinter.

Ethanoic acid + Effervescence occurs. Carbon dioxide
sodium carbonate gas is produced.
Colourless gas released
turns the limewater cloudy.

Ethanoic acid + The black powder of Copper(II) ethanoate
Copper(II) oxide copper(II) oxide dissolves is produced.
to form a blue solution.

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1. With sodium carbonate: Carbon dioxide gas
With magnesium : Hydrogen gas

2. (a) Magnesium ethanoate
(b) Sodium ethanoate
(c) Copper(II) ethanoate

3. (a) 2CH3COOH + Mg → (CH3COO)2Mg + H2
(b) 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
(c) 2CH3COOH + CuO → (CH3COO)2Cu + H2O

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Conclusion:

1. Ethanoic acid reacts with base(copper(II) oxide powder) to
form salt and water.

2. Ethanoic acid reacts metal carbonates (sodium carbonate) to
produce carbon dioxide.

3. Ethanoic acid reacts with reactive metals (magnesium ribbon)
to releases hydrogen gas.

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